Typically, many types of integrated circuits, including non-volatile semiconductor memories such as EPROM, flash EPROM and EEPROM, are designed to operate from a 5 volt (5V) power supply. However, due to the distinct needs of the products that employ integrated circuits, the external power voltage levels supplied to the integrated circuits often have different level. For example, one product for use with a non-volatile memory might supply a positive high voltage (Vpp) of approximately 12V.+-.10% and another product a Vpp of approximately 5V.+-.10%. Similarly, different products might provide Vcc levels of 5V.+-.10% and 3V.+-.10%, respectively.
To accommodate different external power voltage levels, integrated circuit manufacturers include with their chips on-board 5V generator circuits that convert predetermined supply voltages likely to be available to 5V signals. For example, existing on-board 5V generators for flash memories and EEPROMs generate 5V signals from the VPP or VCC signals provided by the programmable electronic devices that employ those chips. However, VPP and VCC signal levels can vary greatly: VPP can be between 5V.+-.10% and 12V.+-.10%, and VCC can be as low as 2.7V. Consequently, chip manufacturers must provide different versions of the chip, each distinguished by a unique 5V generator circuit designed to generate a reliable 5V signal level from a particular VPP or VCC signal level. Moreover, even given a large library of different 5V generator designs, it is possible that none of those designs are compatible with the VCC and VPP levels provided by a particular system environment